大兴安岭东北部兴华渡口群地球物理特征及其地质意义

Geophysical Characteristics and Geological Significance of Xinghuadukou Group in Northeast Daxinganling Mountains

黑龙江省大兴安岭东北部五号桥地区的兴华渡口群属于早—中元古代层状变质岩系,是大兴安岭地区最古老的地层,是金矿的初始矿源层,对金矿的形成具有重要意义。与前震旦纪混合花岗岩相比,兴华渡口群具有密度高、磁性强的特点。地质填图结果表明,兴华渡口群一般呈大小不等的块体产于前震旦纪混合花岗岩中。大兴安岭东北部重力场和磁场的高值异常,表明这一地区存在着规模较大的兴华渡口群。根据重磁异常特征,并对其进行位场换算处理和综合地质解释,推断出兴华渡口群在本区的分布范围和分布形态,确定兴华渡口群基本隐伏在混合花岗岩下,局部地段呈块状沿东西、南北两个方向凸起。兴华渡口群的重磁异常特点及其地质特征为研究该区地质构造及其演化、圈定找矿靶区具有指导意义。

The Xinghuadukou Group belongs to the stratified metamorphic sequences of the Early-Middle Proterozoic. It is the oldest stratum in the Daxinganling Mountains, also the original source of gold mine, having crucial meaning for the forming of gold mine. Comparing with the Presinian migmatitic granites, this Group has higher density and susceptibility. According to the result of regional geological survey, the Xinhuadukou Group generated as shape as large or small blocks in the Presinian migmatitic granites. The distinct gravity and magnetic anomalies in the northeast Daxinganling Mountains indicate the existent of the large scale of Xinghuadukou Group in this area. In terms of the gravity and magnetic anomalies, moreover, through place-field conversion and integrated geological interpretation, deducing the extension and shape distributing of the Xinhuadukou Group, it is shown that the Xinghuadukou Group underlies the granites and has local uplift along SN and EW directions. The geological interpretation of gravity and magnetic anomalies is of significance for studying geological structure and its evolution, and for locating gold deposits.